The present invention relates generally to apparatus and methods for producing waveforms of musical tones, voices or other sounds on the basis of waveform data supplied from memory or the like, and more particularly to an improved waveform producing apparatus and method capable of producing waveforms that faithfully represent tone color variations effected by a player using various styles of rendition (i.e., performing techniques) or various sorts of articulation unique to a natural musical instrument. It should be appreciated that the basic principles of the present invention can be applied extensively to every type of equipment, apparatus and methods having the function of generating musical tones, voices or any other sounds, such as automatic performance devices, computers, electronic game devices and multimedia-related devices, not to mention electronic musical instruments. Also, let it be assumed that the terms "tone waveform" in this specification are not necessarily limited to a waveform of a musical tone alone and are used in a much broader sense that may embrace a waveform of a voice or any other type of sound.
The so-called "waveform memory readout" technique has already been well known, which prestores waveform data (i.e., waveform sample data) coded in a given coding scheme, such as the PCM (Pulse Code Modulation), DPCM (Differential Pulse Code Modulation) or ADPCM (Adaptive Differential Pulse Code Modulation), and then reads out the thus-prestored waveform data at a rate corresponding to a desired tone pitch to thereby produce a tone waveform. So far, various types of "waveform memory readout" technique have been proposed and known in the art, most of which are directed to producing a waveform covering from the start to end of a tone. As one specific example of the waveform memory readout technique, there has been known a scheme of prestoring waveform data of a complete waveform of a tone covering from the start to end thereof. As another example of the waveform memory readout technique, there has been known a scheme of prestoring waveform data of a complete waveform only for a particular portion, such as an attach portion, of a tone presenting relatively complex variations and prestoring a predetermined loop waveform for a sustain portion and the like presenting less variations. In this patent specification, the terms "loop waveform" are used to refer to a waveform to be read out repeatedly, i.e., in a looped fashion.
With the conventional waveform memory readout scheme of prestoring waveform data of a complete waveform of a tone covering from the start to end thereof or prestoring waveform data of a complete waveform only for a particular portion, such as an attach portion, of a tone, however, it has been necessary to prestore a great number of various waveform data corresponding to a variety of styles of rendition (or various sorts of articulation), which would undesirably require a large storage capacity.
Further, although the above-mentioned scheme of prestoring waveform data of a complete waveform of a tone can faithfully express tone color variations effected using various styles of rendition (or various sorts of articulation) unique to a natural musical instrument, it can only reproduce the tone in just the same way as the prestored waveform data and thus would afford very poor controllability and editability. For instance, with this waveform memory readout scheme, it has been extremely difficult to control time-axial and other characteristics of the waveform data, corresponding to a desired style of rendition (or sort of articulation), in accordance with performance data.